Stem assembly for electron discharge devices



Feb. 15, 1938. P. WEIGT STEM ASSEMBLY FOR ELECTRON DISCHARGE DEVICES Filpd Sept. 50, 1936 INVENTOR PAUL WEIGT G Y E N m T T A Patented Feb. 15, 1938 UNITED STATES PATENT OFFICE STEM ASSEMBLY FOR ELECTRON DIS- CHARGE DEVICES Application September 30, 1936, Serial No. 103,226 In Germany October 10, 1935 3 Claims.

It common to pass the exhaust tube of vacuum vessels, such as amplifier tubes, electric bulbs, and the like, through the tubular portion of a reentrant stem. Not only the lead-in wires,

but aiso the exhaust tube is thus enclosed within the glass of the stem tube. There is, however, danger that when the stem tube is pinched to form the press the exhaust tube maybe closed.

In accordance with the invention, a small ring or tube of ceramic material is inserted in the exhaust tube to avoid the danger of closing the inner end of the exhaust tube where it is heated and joins the stem. An upstanding arm or extension may conveniently be formed on the ring to serve as an electrode support.

Figures 1 and 2 illustrate the parts of the stem in assembled relation before heating and compressing the glass around the lead wires and ceramic cylinder; Figure 3 is a sectional view of an envelope bulb with a reentrant stem and exhaust tube assembly embodying this invention; Figure 4 is a stem and exhaust tube assembly embodying thisinvention, and Figures 5, 6 and 7 are end views of the devices shown in Figures 2, 3 and 4, respectively.

In Figure 1 cylinder 1, which is preferably of ceramic material and somewhat longer than the press, is introduced in the end of exhaust tube 2 and is supported upon mounting or jig means 4 on the center line of the stem or stem leg 3. Lead-in wires 5 are held in holes in the jig in an upright position in the annular space between the exhaust tube 2 and stem 3. When heated the stem leg and the glass of the exhaust tube fuse together and onto the cylinder I. When the glass becomes sufiiciently heated it is squeezed between the jaws of a vice or anvil to force the glass into gas tight contact with the lead-in wires to form a so-called press. The ceramic tubing is enclosed with two layers of glass with the spaced current lead-in wires sealed between the concentric rings of glass.

In Figure 2 the diameter of the ceramic tubing 6 is shown considerably larger to accommodate a greater number of current lead-in wires 5 along the periphery of the annular seal. The ceramic cylinder 6 is reduced in diameter as shown at 6' and extended beyond the seal to function as a carrier for electrodes to relieve the lead-in wires of mechanical strain from the electrodes.

In Figure 3, the lead-ins 5 are disposed in the cylindrical junction between the stem and exhaust tube which is of such an internal diameter as to receive in a snug fit ceramic cylinder l0. Exhaust tube II, the wires 5 and the stem tube l2 are arranged in exactly the same manner as in the first example, but here the ceramic cylinder is joined to the glass by continuously turning the glass in a flame until the glass is wetted to the ceramic to obtain an intimate connection between the glass and metal and the ceramic. The flare l2 of the stem is then joined in the usual manner to the rim of an envelope 1O bulb, the bulb is exhausted, and the exhaust tube H sealed oii. On the inner end of the ceramic cylinder may conveniently be provided rods H4 or eyes l5 for supporting metal parts of the electrode assembly.

As shown in Figure 4, the ceramic cylinder may be extended at l6 and joined by glass 18 to metal strips H, which conveniently provide a strong and rugged support for electrodes in the discharge device.

The coeificient of expansion of the ceramic material should approximately correspond to that of the glass, although vacuum tightness is not essential.

I claim:

1. An electron discharge device comprising a tubular glass stem, a concentric exhaust tube joined at one end to said stem along an annular sealing junction, a tubing inserted in and at tached to said exhaust tube at the junction of the tube and the stem whose material has a coefficient of expansion similar to that of glass, and a melting point substantially higher than that of glass, the exhaust tube being fused to said tubing, and a circular series of spaced leadin conductors sealed gas tight in said annular junction.

2. An electron discharge device according to claim 1, characterized in that the tubing consists of ceramic material. 40

3. A sealed glass envelope comprising a bulb portion, a tubular stem extending inwardly from one end thereof, an exhaust tube joined integrally to said stem portion at the inner end thereof and open at its inner end to form an annular Wire anchoring portion, a circular series of spaced lead-in Wires sealed in said annular wire anchoring portion, and a ceramic cylinder in the end of said exhaust tube in registry with said annular anchoring portion to preform said annular portion and maintain the exhaust tube open.

PAUL WEIGT. 

